In general, with the development of electronic communication technologies, a variety of electronic devices are being provided. Such an electronic device increasingly has a tendency to emphasize manipulation easiness for users and a good design. It is diversification of an input device represented by a keyboard or a keypad that is emphasized according to the trend.
The input device has been developed from data processing through the input device, e.g., a keyboard, a keypad, etc., to an available touch panel functioning as both an input device and an output device. The touch panel commonly designates an input device allowing a user to input by touching a screen of a display device without separate input equipment.
The touch panel detects whether the touch is input or not by detecting a capacitance stored in a plurality of formed node capacitors. However, since the capacitance of the node capacitor is changed due to the influence of noise, etc., generated from the display device, there is a possibility of malfunction of the touch panel.